1. Combine the vinegar, shallot, mayonnaise, mustard, salt & pepper to taste in a small nonreactive bowl. Whisk until the mixture is milky in appearance & no lumps of mayonnaise remain. 2. Place the oil in small measuring cup so that it is easy to pour. Whisking constantly, very slowly drizzle the oil into the vinegar mixture. If pools of oil are gathering on surface as you whisk, stop the addition of the oil & whisk the mixture well to combine, then resume whisking in the oil in a slow stream. The vinaigrette should be glossy & lightly thickened, with no pools of oil on its surface. 3. Add the herbs just as you finish & whisk to combine. 4. Pour the vinaigrette into a mason jar & cover with lid. This recipe can be made a couple of hours in advance & left at room temperature. Store any leftover vinaigrette in the refrigerator for 2-3 days.